The next thing you want to make sure of is--DO NOT re-new or reinstall Norton!
Years ago, Norton use to be good but now its such a memory hog that it sucks the life, memory and ram out of your computer.
Try a different anti-virus such as Micro Trend or AVG. I installed AVG onto my XP and the best thing is--it's free and works great!
http://free.avg.com/